Exercise bike



FIG. 1 is a front, left side, and top perspective view of an exercise bike showing the new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a rear elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The portions of the design shown in broken lines show unclaimed subject matter. 

CLAIM The ornamental design for an exercise bike, as shown and described. 